Gyroscope, an apparatus applying inertia principle to measure rotary angle or angular velocity, is mainly applied in the guidance of military, aviation, and navigation, etc. According to operational principle, gyroscope may be divided to two kinds: rotor-typed gyroscope and vibratory gyroscope driven by static electricity.
As shown in FIG. 1, which is a single-axial beam-typed gyroscope (U.S. Pat. No. 4,499,778: Flexure Mount Assembly for A Dynamically Tuned Gyroscope and Method of Manufacturing Same). Said gyroscope 10 is a traditional beam-typed rotary gyroscope, which is capable of single-axial measurement and assembled by plural machined elements 16, 18. Traditional rotor-typed gyroscope 10 is designed by applying the conservation principle of angular momentum so as to obtain the angular speed of rotation, so there are many problems involving complicated structures and bearing friction, such that there are many shortcoming existing in traditional gyroscope, such as: expansive price, heavy weight, and short lifetime, etc.
Different from the design principle of traditional rotor-typed gyroscope, the vibratory gyroscope is designed by the vibration principle of an elastic body; that is, two vibration modes, originally possessed by the gyroscope configuration, normal to each other and having same frequency, are applied as the driving and sensing models for enhancing the system's sensitivity. Since the structure of said vibratory gyroscope is simple and without moving element, such as: bearing, so it is extremely suitable for mass production with micro-machining technique so as to lower down the manufacturing cost. Therefore, since the vibratory micro-gyroscope has the advantages of low cost, superior performance and microscopic size, so it has been gradually applied in wide field. Besides, the vibratory micro-gyroscope is designed by the signal noise ratio of signal checking-out circuit and by the optimal configuration, so it has high-classed sensitivity to have the potential in becoming commercialized sensing element.
As shown in FIG. 2, which is a ring-typed vibratory gyroscope 20 (U.S. Pat. No. 5,450,751: Microstructure for Vibratory Gyroscope). The vibratory gyroscope 20 is arranged in a base 22 and is comprised of ring 24, hub 25 and plural semi-supporting spoke 26 distributed in equal distance and in radial direction. There are plural charge conductive sites 23 arranged around the circumference of the ring 24. The ring 24 and spoke 26 are all manufactured by the Micro Electric Mechanical System (MEMS) technology with high aspect ratio. The structural altitudes of both the ring 24 and the spoke 26 are same. Each different zones of the ring 24 provides the needed inducing area to the vibratory gyroscope 20 as static-electricity driving and capacitance sensing electrodes. Its inducting manner is accomplished by the inter-induction between the different sections of the ring 24 and the plural sensing/driving electrodes 23.
Again, please refer to FIG. 3, which is a ring-typed vibratory gyroscope 30 (U.S. Pat. No. 5,547,093: Method of Forming A Micromachine Motion Sensor), of which structure is same as that of the vibratory gyroscope 20 shown in FIG. 2, and which includes an ring 34, center post 35, and plural arcuate springs 36 distributed in equal distance and in radial direction. There are plural electrodes 33 arranged around the circumference of the ring 34. The ring 34 and arcuate springs 36 are all manufactured by the MEMS technology with high aspect ratio. The structural altitudes of both the ring 34 and the arcuate springs 36 are same. Each different zones of the ring 34 provides the needed inducing area to the vibratory gyroscope 30 as static-electricity driving and capacitance sensing electrodes. Its inducting manner is accomplished by the inter-induction between the different sections of the ring 34 and the plural sensing/driving electrodes 33.
Furthermore, please refer to FIG. 4, which shows a suspending-beam-typed vibratory gyroscope 40 (U.S. Pat. No. 4,381,672: Vibration Beam Rotation Sensor), which is machined and manufactured by MEMS technology, and which mainly includes a suspending arm beam 41 that is arranged on base electrode 42. There are beam electrodes 43 covered at the bottom and the side edge of the suspending arm beam 41. Oscillator circuit 44 drives voltage between the base electrode 42 and the beam electrode 43 to make the suspending arm beam 41 first generate vertical reciprocating motion in up and down directions, and the suspending arm structure is then converted to horizontal vibration operated by Coriolis force. The pressure sensing devices arranged at two sides of the suspending arm beam 41 senses the horizontal vibration distance to obtain the acceleration value of the rotating angle.
In summarizing each ring-typed vibratory gyroscope shown from FIG. 2 through FIG. 4, it may find that the rings 24, 34 of the vibratory gyroscopes 20, 30 and the sensing electrodes must adopt particular manufacturing process of high aspect ration of twenty. This design can not be fulfilled by common MEMS technology. In addition, since the activation of the vibratory gyroscope is driven and sensed by two coplanar elliptic modes, of which phases are differentiated by 45 degrees, so the aforementioned gyroscopes 20, 30, 40 are all used for single-axial sensing only.